Foams are generally understood to represent materials in which a gas, such as air, is finely dispersed in a liquid in a form that is stable over some time. The liquid is found in the form of thin films between the bubbles. The stabilizing element of such gas dispersions is the surface tension of the liquid phase. The surface tension can be influenced by the presence of surface-active agents in the fluid phase, which help to stabilize the films against collapse. These foams are generally referred to as closed pore foams, as there is no connection between the gas spaces of each individual bubble. If the liquid films are stabilized by other means, e.g. by chemical reactions that transform the liquid phase into a viscoelastic solid, then the formation of open pore foams is possible, in which the fluid bridges are removed in a controlled manner, e.g. by evaporation or other processes. The transformation of the liquid films into a viscoelastic solid material also serves to effectively stabilize the foams against rapid collapse.
It is an object of the present invention to provide improved hemostatic foams which can be safely injected into tissue voids with low visibility and which are effective with no need for approximation. In addition, it is important that such a foam hemostat does not present a risk of obstruction or compression of pressure sensitive organs or tissues due to excessive swelling. Such a foam should be specifically applicable in neuro/spine, laparoscopic and cardiovascular surgery.